In recent years, a large number of multi-functional digital copying machines, which has functions such as a copying machine, a facsimile and printer in a unified manner, have been commercialized. These digital copying machines are used with a lot of external apparatuses being connected to form a network, and a large amount of image information is inputted thereto from these external apparatuses.
The above-mentioned digital copying machine requires a storage device with a large capacity for storing the inputted image information. However, if the storage device is constituted by semiconductor memories, and if the large amount of image information is all managed by the semiconductor memories, a problem of high costs is raised. Therefore, in general, disk memory devices, such as, for example, hard disks, are adopted as the storage devices. These disk memory devices successively record image information that is forwarded from the external apparatuses, and also store information, such as filing, for a long time.
With respect to processing methods, etc., for outputting data by using a disk memory device with a large capacity as a temporary storage device for a plurality of pieces of input data, for example, U.S. Pat. No. 5,535,017 has suggested some of those methods.
However, in such conventional arrangements, since the disk memory device records and manages a large amount of image information, stored in the disk memory device, might disappear in the event of a failure in the disk memory device.
For example, in the multi-shot function in which image data, which corresponds to a plurality of sheets of documents that have been read, is automatically magnified or reduced so as to output it on one sheet of recording paper, a plurality of pieces of image information have to be successively stored in the disk memory device. Further, in the filing function in which data of documents to be shared in an office, etc., is stored in a shared manner on the disk memory device, the image information is stored and maintained for a long time.
Therefore, if the disk memory device has broken down during the use of the above-mentioned functions, image information which has been processed so far might become useless in the multi-shot function, or the importance of filing might be blemished in the filing function. In the event of a failure, the larger the capacity of the disk memory device, the greater the seriousness of these problems.